Problem: Constraints

* H is an integer between 2 and 50 (inclusive).
* W is an integer between 2 and 50 (inclusive).
* s_{i, j} is `.` or `#` (1 \leq i \leq H, 1 \leq j \leq W).
* s_{1, 1} and s_{H, W} are `.`.

Input

Input is given from Standard Input in the following format:


H W
s_{1, 1}s_{1, 2}s_{1, 3} ... s_{1, W}
s_{2, 1}s_{2, 2}s_{2, 3} ... s_{2, W}
:   :
s_{H, 1}s_{H, 2}s_{H, 3} ... s_{H, W}


Output

Print the maximum possible score that Snuke can achieve, or print -1 if the game cannot be completed.

Examples

Input

3 3
..#
#..
...


Output

2


Input

3 3
..#
..
...


Output

2


Input

10 37
.....................................
...#...####...####..###...###...###..
..#.#..#...#.##....#...#.#...#.#...#.
..#.#..#...#.#.....#...#.#...#.#...#.
.#...#.#..##.#.....#...#.#.###.#.###.
.#####.####..#.....#...#..##....##...
.#...#.#...#.#.....#...#.#...#.#...#.
.#...#.#...#.##....#...#.#...#.#...#.
.#...#.####...####..###...###...###..
.....................................


Output

209

Solution (in PYTHON3):

Solution:
H,W = (int(i) for i in input().split())
grid = ['#'*(W+2)]+['#'+input()+'#' for i in range(H)]+['#'*(W+2)]
smap = [[-1 for i in range(W+2)] for i in range(H+2)]
q = []
dot = 0
angle = [[1,0],[-1,0],[0,1],[0,-1]]

for i in grid:
  dot += i.count('.')

smap[1][1] = 1
q.append([1,1])

while len(q) > 0:
  pos = q.pop(0)
  cnt = smap[pos[0]][pos[1]] + 1
  for a in angle:
    if grid[pos[0]+a[0]][pos[1]+a[1]] == '.' and smap[pos[0]+a[0]][pos[1]+a[1]] == -1:
      q.append([pos[0]+a[0],pos[1]+a[1]])
      smap[pos[0]+a[0]][pos[1]+a[1]] = cnt

print(-1) if smap[H][W] == -1 else print(dot - smap[H][W])